Once you understand something, it looks trivial.
I don't know if this is generally the case, but it certainly is for me, and I have seen it in others. It seems to occur most often with math. Everything in math is TrivialOnceUnderstood.
It may even be used to check that somebody has understood something. If he thinks it is trivial, he probably has.
However, some things are TrivialOnceMisunderstood?. This is often due to understanding a specific case, but not the general case or vice versa.
An example from math: PeanoAxioms? (http://en.wikipedia.org/wiki/Natural_number#Peano_axioms) are trivial in that they 'just' state what we all know about natural numbers. But formalizing this 'obvious' intuition is exactly the important part. -- .gz
See also AhaMoment, YouCantLearnSomethingUntilYouAlreadyAlmostKnowIt